Imagination and control

[From Rick Marken (2006.03.12.1015)]

Martin Taylor (2006.03.10.10.34) --

But, and here's the problem, "Imagination Mode" is ordinarily treated as a feedback path in a perceptual control loop. It is generated by a simulation of what the consequence would be if one performed a certain act.

Actually, an imagined perception is modeled as the playing of the reference signal right back into the perceptual path of the system sending that reference signal. So an imagined perception is just perceiving what you want.

Having just written what I said above, it seems clear to me that the World Model in the feedback loop of a control system is not the only World Model -- or else it's in the wrong place. The World Model that predicts the effects of one's control actions to produce an imagined result must also include the predictable changes inthe world that are not affected by one's own actins. One's actions are imposed on what the world would do if we abstained from control, which is the situation discussed above.

I'm going to be doing a section on imagination soon in my Cognition course so this little discussion has been helpful. One of the most influential studies of imagination is the Shepard/Metzler "Mental rotation" study. What you seem to have her is a situation where, in order to determine if two pictured objects are the same or not, you imagine what would happen to one of the objects if it were actually rotated. You don't actually rotate the object, so the feedback path connecting your actions (applying a rotation) to the resulting perception (or a rotated form) does not go through the environment. So you are controlling a lower level perception (of rotation) in imagination as the means of controlling for the higher level perception of a relationship (sameness) between the pictured objects. I think it's interesting that people seem to do, in imagination, what they would do with the objects themselves (rotation) in order to determine if they are the same or not. This is interesting because you might imagine that people could instantly imagine the object in the rotated state in order to make the comparison. After all, there are no physical constraints on the object in imagination. But Shepard and Metzler show that the time required to evaluate the relationship between objects is proportional to the angular difference between the objects, which suggests that the imagined rotation is constrained in the same way as the physical rotation; it takes longer to mentally rotate in object through 160 degrees than it does to mentally rotate the object through 60 degrees, justas it necessarily takes longer to physically rotate an object through 160 as compared to 60 degrees.

The textbook I am using describes other studies that also suggest that imagined means of achieving higer-level goals are constrained in the same way they would be if the means (lower level perceptions) were controlled via the feedback path. For example, answering questions about higher level properties of objects (like "does the tiger have spots?") takes longer if these objects are imagine as being confined in small rather than as large spaces. As in the "perception" mode it is harder to "see" the properties of small as compared to large objects.

These results suggest to me that the hierarchical control of imagination is similar to the hierarchical control of perception, except that, when controlling in imagination, there are no disturbances that occur when you are controlling the lower level perception as the means to controlling the higher level one.

It seems to me that there should be some variation of the Shepard/Metzler study that could be done based on an understanding of their results in terms of control theory. I'd be interested in hearing what others, particularly the experimentalists, think about this.

Best regards

Rick

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